The invention relates to a system and method for optimizing production from a rod-pumping system.
Rod-pumping systems such as sucker-rod type pumping units and the like are widely used in the petroleum industry in order to assist in recovering fluid from wells extending into subterranean formations containing such fluid. A typical sucker-rod unit includes a sucker-rod string which extends into the well and a motor or other structure at the surface for generating an up and down movement of the rod string in order to operate a downhole pump.
A variety of malfunctions can occur with such systems, including worn pumps, broken sucker-rods, split tubing, stuck valves and the like. These malfunctions can be caused by normal wear and tear, and can be accelerated and/or exacerbated by abnormal pumping conditions.
A useful tool in evaluating the operating state of a rod-pumping system is the dynagraph chart, which is the rod load as a function of position of the rod string. Dynagraph charts are typically obtained using load and position cells, but three main problems arise using this technology. First, the load cell calibration procedure is difficult and must be done frequently. Second, temperature adjustments must be carried out. Third, great care must be taken with the electronic devices each time field work is necessary. Due to these problems, obtaining dynagraph charts has been limited to only certain wells where production benefits justify these difficulties.
It is the primary object of the present invention to provide a system and method whereby dynagraph relationships can be widely used to optimize and enhance production from rod-pumping systems without the aforesaid difficulties.
It is a further object of the present invention to provide such a method and system which can detect potential fault conditions before they occur so that production interruptions and excessive equipment wear can be avoided.
Other objects and advantages of the present invention will appear hereinbelow.
In accordance with the present invention, the foregoing objects and advantages have been readily attained.
According to the invention, a method is provided for optimizing production from a rod-pumping system, which method comprises the steps of providing a well having a rod pumping system for pumping a fluid from a downhole location of said well to a surface location of said well; providing a mathematical model for determining a dynagraph relationship for said well from power consumption of said rod-pumping system; measuring power consumption per cycle of said rod pumping system; determining a downhole dynagraph relationship from said power consumption per cycle and said model; measuring real time values of wellhead pressure; and determining an optimum operating condition for said rod pumping system from said downhole dynagraph relationship and said real time values.
In further accordance with the present invention, a system has been provided for optimizing operation of a rod pumping system in a well for pumping fluid from a downhole location of said well to a surface location of said well, comprising: a power sensor for measuring instantaneous power consumption of said rod-pumping system; a pressure sensor for measuring real time wellhead pressure of said well; and control unit communicated with said power sensor and said pressure sensor and programmed with a mathematical model for determining a dynagraph relationship for said well from power consumption of said rod pumping system per cycle, said control unit being adapted to: determine a downhole dynagraph relationship from said power consumption per cycle and said model; and determine an optimum operating condition for said rod pumping system from said downhole dynagraph relationship and said real time wellhead pressure; whereby optimum operating conditions are determined from dynagraph relationships without directly measuring said dynagraph relationships.